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<li class="toctree-l4 current"><a class="current reference internal" href="#"><code class="docutils literal notranslate"><span class="pre">bagof/3</span></code></a></li>
<li class="toctree-l4"><a class="reference internal" href="findall_3.html"><code class="docutils literal notranslate"><span class="pre">findall/3</span></code></a></li>
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  <p class="align-right"><strong>built-in method</strong></p>
<section id="bagof-3">
<span id="methods-bagof-3"></span><span id="index-0"></span><h1><code class="docutils literal notranslate"><span class="pre">bagof/3</span></code><a class="headerlink" href="#bagof-3" title="Link to this heading"></a></h1>
<section id="description">
<h2>Description<a class="headerlink" href="#description" title="Link to this heading"></a></h2>
<div class="highlight-logtalk notranslate"><div class="highlight"><pre><span></span><span class="k">bagof</span>(<span class="nv">Template</span>, <span class="nv">Goal</span>, <span class="nv">List</span>)
</pre></div>
</div>
<p>Collects a bag of solutions for the goal for each set of instantiations
of the free variables in the goal. The order of the elements in the bag
follows the order of the goal solutions. The free variables in the goal
are the variables that occur in the goal but not in the template. Free
variables can be ignored, however, by using the <code class="docutils literal notranslate"><span class="pre">^/2</span></code> existential
qualifier. For example, if <code class="docutils literal notranslate"><span class="pre">T</span></code> is term containing all the free
variables that we want to ignore, we can write <code class="docutils literal notranslate"><span class="pre">T^Goal</span></code>. Note that the
term <code class="docutils literal notranslate"><span class="pre">T</span></code> can be written as <code class="docutils literal notranslate"><span class="pre">V1^V2^...</span></code>.</p>
<p>When there are free variables, this method is re-executable on
backtracking. This method fails when there are no solutions, never
returning an empty list.</p>
<p>This built-in meta-predicate is declared as a private method and thus
cannot be used as a message to an object.</p>
</section>
<section id="meta-predicate-template">
<h2>Meta-predicate template<a class="headerlink" href="#meta-predicate-template" title="Link to this heading"></a></h2>
<div class="highlight-logtalk notranslate"><div class="highlight"><pre><span></span><span class="k">bagof</span>(<span class="o">*</span>, <span class="o">^</span>, <span class="o">*</span>)
</pre></div>
</div>
</section>
<section id="modes-and-number-of-proofs">
<h2>Modes and number of proofs<a class="headerlink" href="#modes-and-number-of-proofs" title="Link to this heading"></a></h2>
<div class="highlight-logtalk notranslate"><div class="highlight"><pre><span></span><span class="k">bagof</span>(<span class="o">@</span>term, <span class="o">+</span>callable, <span class="o">-</span>list) <span class="o">-</span> zero_or_more
</pre></div>
</div>
</section>
<section id="errors">
<h2>Errors<a class="headerlink" href="#errors" title="Link to this heading"></a></h2>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">Goal</span></code> is a variable:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">instantiation_error</span></code></div>
</div>
<div class="line"><code class="docutils literal notranslate"><span class="pre">Goal</span></code> is neither a variable nor a callable term:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">type_error(callable,</span> <span class="pre">Goal)</span></code></div>
</div>
<div class="line"><code class="docutils literal notranslate"><span class="pre">Goal</span></code> is a call to a non-existing predicate:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">existence_error(procedure,</span> <span class="pre">Predicate)</span></code></div>
</div>
</div>
</section>
<section id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Link to this heading"></a></h2>
<div class="line-block">
<div class="line">To find a bag of solutions in the context of the object or category containing the call:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">bagof(Template,</span> <span class="pre">Goal,</span> <span class="pre">List)</span></code></div>
</div>
<div class="line">To find a bag of solutions of sending a message to <a class="reference internal" href="../../glossary.html#term-self"><span class="xref std std-term">self</span></a>:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">bagof(Template,</span> <span class="pre">::Message,</span> <span class="pre">List)</span></code></div>
</div>
<div class="line">To find a bag of solutions of sending a message to an explicit object:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">bagof(Template,</span> <span class="pre">Object::Message,</span> <span class="pre">List)</span></code></div>
</div>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference internal" href="findall_3.html#methods-findall-3"><span class="std std-ref">findall/3</span></a>,
<a class="reference internal" href="findall_4.html#methods-findall-4"><span class="std std-ref">findall/4</span></a>,
<a class="reference internal" href="forall_2.html#methods-forall-2"><span class="std std-ref">forall/2</span></a>,
<a class="reference internal" href="setof_3.html#methods-setof-3"><span class="std std-ref">setof/3</span></a></p>
</div>
</section>
</section>


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